Various low slope roofing systems have been developed for buildings and the like. Such low slope roofing systems commonly include a structural deck that is metal or concrete. The deck may then be covered with a layer of insulation, and the insulation is then covered with a waterproof membrane. Wind acting on the building structure may cause a substantial uplift force acting on the roof membrane. The membrane in known systems may be secured utilizing ballast such as gravel to prevent uplift of the membrane. Alternately, the membrane may be adhesively bonded with hot asphalt, or flammable solvent based contact bond adhesives. Other known systems utilize a two component, sprayable polyurethane foam adhesive primarily composed of di-isocyanate and polyol compounds. Such polyurethane foam arrangements utilize a spray gun that mixes the components and sprays the liquid mixture on the substrate. The membrane is immediately applied and the adhesive mixture then expands, or foams, and solidifies to form a bond. However, such polyurethane foam adhesive arrangements may suffer from numerous drawbacks. For example, the spraying of the polyurethane adhesive produces a potentially hazardous aerosol, requiring use of protective suits, respiratory protection, or the like in order to protect those spraying the adhesive and applying the roof membrane. Furthermore, inclement weather conditions also may create problems with such systems due to high wind or low temperatures. The spraying equipment required to spray such foam is generally quite large and heavy, thereby requiring substantial effort to position the equipment on the building roof. Such equipment also includes numerous components such that it is also quite expensive and often difficult to maintain.
Flammable, solvent based contact bond adhesives require that adhesive be spread on both bonding surfaces by brush, roller, or spray, and that they also remain in an unassembled condition until the majority of the solvent evaporates into the atmosphere. The coated substrates are then assembled and compressed with a metal roller to set the bond. Such applications of roof membrane are labor intensive, time consuming, and present certain occupational hazards to personnel breathing hazardous solvent vapors. Such “solvent release” type adhesives also contaminate the atmosphere with volatile organic compounds. The solvents may also become trapped below the membrane, causing blisters and delamination requiring repair.
Such existing polyurethane foam adhesive systems and solvent based adhesive systems may provide sufficient bond strength to meet roofing industry standards. However, building roof structures may experience uplift forces exceeding such standards, such that substantial damage may be incurred, even by buildings that meet standards. In addition to the damage to the building, items within the building such as stored products or other inventory, production equipment, office equipment, computers, and the like may also suffer serious damage. Due to the large numbers of buildings utilizing membrane type roof structures, such damage can be extremely costly, especially in geographic areas that experience hurricanes or other high wind conditions.
Although moisture curing adhesives have been used to bond structural components such as capping, metal edges, skylights, roof insulation and the like, it is not believed that such adhesives have heretofore been utilized to bond waterproof roof membranes to low slope roof substrates.